In constructing machinery which must convert rotary motion into translinear motion or vice versa, for instance in such machines as internal combustion engines, compressors, and piston type pumps, the preferred configuration for such conversion of motion is the use of a linear driveshaft rotatably mounted in the machine and having one or more eccentric journals.
Connecting rods mounted on the eccentric journals by bearings and having pistons at the opposite ends thereof may be driven in a linear direction, for example in a cylinder, by rotation of the crankshaft eccentric journals.
Construction of crankshafts in the past have evolved from casting and/or forging of a single piece crankshaft having integral journals and webs formed thereon. Due to the complex geometry of such a shaft, arising from the webs, notches, and radiuses, the prediction of internal stresses in the shaft has been very unsuccessful, therefore the thickness of the shaft and journal areas in particular was greatly overdesigned to compensate for unknown stresses in the stress concentration areas.
Efforts have been made to fabricate a crankshaft by attaching the eccentric journals to the longitudinal shaft. These efforts involved attempts to duplicate the complex geometry of the cast one-piece crankshaft and as a result, made no improvement in the stress analysis problem. As a result, just as much material was used in these fabrications as is used in the cast shaft and the only gain was in the elimination of the casting step. Since the time involved in the complex fabrication process offset the advantage gained, this was never an economical method of manufacturing the crankshaft.
This invention discloses a crankshaft and its method of manufacture which greatly reduces the time of manufacture, allows a highly accurate stress analysis to be obtained, and greatly reduces the amount of excess material needed for strength. The invention involves a one-piece straight shaft upon which is pressed eccentric discs to act as journals.